Simplify travis.yml

Do not need the parts in travis if using defaults.

Author: lowks

.travis.yml

@@ -1,10 +1,5 @@
 sudo: false
 language: elixir
-script:
-  - mix test
-before_script:
-  - mix local.hex --force
-  - mix deps.get
 after_script:
   - mix deps.get --only docs
-  - MIX_ENV=docs mix inch.report
+  - MIX_ENV=docs mix inch.report